Gaseous electric discharge lamp device



W. UYTERHOEVEN ET AL, fi fi GASEOUS ELECTRIC DISCHARGE LAMP DEVICE FiledApril 25, 1934 1 i 1 I I 1 E' i ,2 fi 6 t t 26 E 1 1 Q Q t i i INVENTORSBY 88M AT ORNEY Fatented @ct. 6, W36

QGASIEQUS ELECTRIC DISCRGE LAMP DEVICE Willem Ilyterhoeven,

Cornelis Wei-burg,

Johannes Bruijnes, and Eindhoven,

Netherlands,

assignors to General Electric Company, a corporation of New YorkApplication April 23, 1934, Serial No. 722,010 In the Netherlands April29, 1933 6 Claims.

The present invention relates to gaseous electric discharge lampdevices.

A gaseous electric discharge lamp device having a gaseous fillingconsisting of a rare gas and a metal vapor emits light the spectrum ofwhich contains rays characteristic of the gas and of the vapor providedthe vapor is at a proper pressure. The light emitted by a gaseouselectric discharge lamp the gaseous atmosphere of which comprises neonand mercury vapor, for example, approximates white light. The vaporpressures of such a lamp must be controlled within narrow limits inorder to obtain a balance between the light emitted by the vapor andthat emitted by the gas. Control of the metal vapor pressure is obtainedby controlling the temperature of the vaporizable material. Thevaporizable material is placed in an off set chamber communicating withthe container of the lamp device and a heating element is mounted inoperative relation to said ofi-set chamber to heat the vaporizablematerial to a desired temperature.

This structure, while effective for a lamp the gaseous atmosphere ofwhich comprises one metal vapor, is not practical when the gaseousatmosphere comprises two or more metal vapors which are excited toluminescence during the operation of the lamp. In this case it isnecessary to heat the vaporizable metals to different temperatures inorder to obtain an eifective pressure of each metal vapor. This is notpractical since the pressure of the metal vapor is controlled hy thelowest temperature of the container and heating one vaporizable metal toa higher temperature than another metal would be futile since the vaporpressure of all the metals in the container is determined by the lowesttemperature of the container.

The object of the present invention is to provide a method of and ameans for operating a gaseous electric discharge lamp the gaseousatmosphere of which comprises two or more different vaporizable metalswhereby both metals are luminescent during the operation of the device.Another object of the invention is to provide a gaseous electricdischarge lamp emitting light comprising rays characteristic of two ormore metal vapors. Still further objects and advantages attaching to thedevice and to its use and operation will be apparent to those skilled inthe art from the following particular description.

In accordance with this object the invention comprises an electricdischarge tube which contains the vapor of at least two metals and whichis energized by an alternating-current source of normal networkfrequency, (for instance 40 to 60 cycles), while the discharge current,which changes according to the frequency of the current source, isregulated in such manner that in the case of a smaller current (in therising and dropping branches of the current curve), the light of one ofthe metal vapors predominates, while in the case of a, higher currentvalue (at points located higher in the current curve), the light of theother metal vapor predominates. In that manner, a light of a difierentcolor is obtained alternately. The frequency of this change in color isat least twice the frequency of the alternating-current source. It ispractically impossible to see the color change of the emitted light whennormal network frequencies are used, so that the light has a mixed color(it is of course possible to determine the color change by means of astroboscope).

In general it is recommended to use in the discharge tube a mixture ofmetal vapors, of which one has both a lower ignition voltage and also alower vapor pressure than the other metal vapor.

In order to obtain a mixed light which contains yellow, blue, and greenrays, a discharge tube is used which contains sodium vapor and mercuryvapor, for example. The current is then adjusted to such a value that ata lower, current the sodium light predominates, while at a highercurrent the mercury light predominates. The sodium light has a yellowcolor and the mercury light a green-blue color, so that the combinedlight will contain both yellow lines and also green and blue lines.

In practice, a starting gas is present in the discharge tubes, since theignition is thereby facilitated. In many cases the discharge current canbe given such a magnitude that during a part of every cycle the light ofthis gas appears. Forinstance, if in a discharge tube both neon and alsosodium vapor and mercury vapor are present, then the discharge currentis regulated in such manner that the value thereof during each cycle issuch that the neon light appears temporarily. In some cases it isadvisable to make the mercury vapor unsaturated. The neon light adds redrays to the yellow-blue-green light.

The invention will be readily understood by an inspection of the drawingaccompanying and forming part of this specification and. a perusal ofthe following detailed description thereof. In the drawing,

Fig. 1 is a front elevatlonal, partly sectional view of one embodimentof the invention, and a circuit therefor,

Fig. 2 represents the current flow through the device illustrated inFig. 1, and

Fig. 3 represents an increased current flow through the deviceillustrated in Fig. 1.

Referring to Fig. l of the drawing the new and novel lamp unit comprisesa U-shaped discharge tube 1 having sealed in each end thereof athermionic electrode 2 and a cylindrical anode 3 which surrounds thethermionic electrode 2. Said electrodes 2 comprise a coiled tungstenfilament, a nickel filament wrapped around said tungsten filament and acoating of electron emitting material, such as barium oxide. The tubehas a gaseous filling therein comprising neon at a pressure of a fewmillimeters and a quantity of sodium and mercury. The discharge tube issurrounded by a double-walled cover 4 which has heat-insulatingproperties, while the space between the two walls of this cover has beenevacuated. The two glow electrodes 2 are energized by the transformer 5.The primary windings of these transformers are connected to thealternating-current network 6 of normal frequency, for instance, 50cycles. The current-supply wires of the anodes 3 are connected to one ofthe current-supply wires of the glow electrodes 2. These are connectedto the network 6, while a choke coil 1 is connected in series with thedischarge tube as a stabilization impedance.

During the operation of the discharge tube, the current which flowsthrough the tube will have approximately the shape shown in Figure 2.

The current is adjusted in such a way that during the time intervalslocated between 151 and t2, and between its and t4, the sodium lightpredominates, while during the time intervals between t2 and t3, themercury light is in excess which can be determined very readily by meansof a stroboscope. The relation between the time intervals can be alteredby changing the current values. Figure 2 shows that the color changesfour times during each alternating current cycle. These color changescannot be detected by the naked eye, so that the light emitted by thedischarge tube creates the impression of consisting of the combinationof the yellow sodium light and the blue-green mercury light. If it isdesired to have red rays instead of the yellow sodium light, then adischarge tube is used which contains for instance potassium andmercury.

Take, for example, a discharge tube with a gaseous filling of neon,sodium and mercury, with an electrode spacing of 40 cm., and an internaldiameter of 21 mm., energized by an alternating current source with afrequency of 50 cycles and an effective voltage of 220 volts and havingthe choke coil adjusted in such a way that the effective value of thedischarge current is 1.4 amperes. In this case the time interval betweent2 and is, during which the mercury light predominated, last of a halfA. C. cycle, that is, 0.01 second. During the time interval between inand t1, (leaving the short dark period between t4 and t1 out ofconsideration), the sodium light predominates.

The current may be increased to such an extent that the neon lightappears at the highest value of the current. The curve of this currenthas been given by way of example in Figure 3. During the time intervalsbetween t1 and 122, or between t3 and t4, the sodium light predominates,and during the time intervals between 152 and is, or between is and t3,the mercury light is in excess, while finally between is and is, theneon light is the strongest. In this manner a mixed light is obtainedwhich contains yellow, blue, green, and red rays and which approximateswhite light very closely. In order to influence the relative intensityof the various colored light rays, it is preferable that the mercuryvapor be kept unsaturated during the operation of the device by limitingthe quantity of mercury therein.

One of the advantages of the invention lies in the fact that it ispossible by means of an electric discharge tube to produce mixed lightwith a very high efliciency.

It will be understood of course that in a com plete lamp unit a base isprovided to support the heat conservator 4 and the container l and. aheat insulating means is provided between the container 1 and the heatconservator 4 to close off the space therebetween from the outsideatmosphere. These elements have been omitted from the drawing forpurposes of simplicity of illustration.

What we claim as new and desire to secure by Letters Patent of theUnited States is:-

1. The method of operating a gaseous electric discharge lamp having agaseous atmosphere comprising two metal vapors which consists inregulating the alternating current to said device to a frequency of 40cycles per second at the minimum and to a magnitude such that one ofsaid vapors is predominantly luminescent during part of each cycle andanother of said vapors is predominantly luminescent during another partof each cycle.

2. The method of operating a gaseous electric discharge lamp having agaseous atmosphere comprising two metal vapors having a difierentpressure at the same temperature which consists in regulating thealternating current to said device to a frequency of 40 cycles persecond at the minimum and to a magnitude such that one of said vapors ispredominantly luminescent during part of each cycle and another of saidvapors is predominantly luminescent during another part of each cycle.

3. The method of operating a gaseous electric discharge lamp having agaseous atmosphere comprising mercury and sodium vapor which consists inregulating the alternating current to said device to a frequency of 40cycles per second at the minimum and to a magnitude such that one ofsaid vapors is predominantly luminescent during part of each cycle andanother of said vapors is predominantly luminescent during another partof each cycle.

4. The method of operating a gaseous electric discharge lamp having agaseous atmosphere comprising a rare gas, mercury and sodium vapor whichconsists in regulating the alternating current to said device to afrequency of 40 cycles per second at the minimum and to a magnitude suchthat one of said vapors is predominantly luminescent during part of eachcycle and another of said vapors is predominantly luminescent duringanother part of each cycle and said gas is predominantly luminescentduring another part of each cycle.

5. The method of operating a gaseous electric discharge lamp having agaseous atmosphere comprising neon, mercury and sodium vapor whichconsists in regulating the alternating current to said device to afrequency of 40 cycles per second at the minimum and to a magnitude suchthat one of said vapors is predominantly luminescent during part of eachcycle and an- 5 unsaturated.

6. In combination a gaseous electric discharge lamp comprising acontainer, electrodes sealed therein, a gaseous atmosphere thereincompris ing a rare gas, an easily vaporizable material and 10 a dimcultyvaporizable material, a choke coil connected in series with. said lamp,a 220 volt, 50 cycle current source for said lamp, said choke coilregulating the discharge current in said lamp to approximately 1.4amperes, said gaseous constituents being excited to luminosity atdifferent times in each cycle of said current source.

WIILEM UYTERHOEVEN. JOHANNES BRUIJNES. CORNELIS VERBURG.

